> Alexander Varakin wrote:
> >
> > Hi to all.
> >
> > I need one linear amplifier and three comparators in my PIC project. I
> > intend to use a quad comparator LM339. Can I use a spare comparator of
this
> > chip as a  linear amplifier? The magnitude of the amplifier must be
about
> > 100, frequency range 100-5000Hz.
>
> Rather use an amplifier as a comparator. Use a TL074 quad op-amp.
> The input impedance is 1.6Tohm and the open loop gain is enough
> to make it work exactly the same as a 'comparator' chip (no feed-
> back resistor from output to -input).
>
> --
> Friendly Regards
>
> Tjaart van der Walt
Thank you for advice.I will see TL074's datasheet. I know about this way,
but the comparators for my project must have quite high speed (response
time 1us) and be very cheap. As far as I know quad op-amps have internal
frequency correction which makes op-amp slow. I compared LM324(quad op-amp)
and LM339(quad comparator), they have just the same price, but response
time of LM324 is about 5us, response time of LM339 is 1us.
Regards
Alexander.